On 2025-02-10 02:15, martin rudalics wrote:
>> To handle this I would need to add checks against the down-mouse-1
>> keybinding before setting the mouse icon.  I'm just worried about
>> performance here since looking up the keymap would get run on mouse
>> motion.
> 
> I think there's no reason to bother about 'ruler-mode'.  IIRC, apart
> from the scroll bar, the ruler has no "empty space" and dragging should
> mostly happen in a horizontal fashion.

Attached is a patch that adds the vertical scroll icon for header and 
tab lines.  I also altered ruler-mode so that dragging works with it as 
well as it has no real reason to block dragging AFAICT.  Similar changes 
would be needed in other packages if the desire is to be aligned with 
the newly shown drag icon.  The only way to outright hide the drag icon 
is to add a keymap via text properties, which is already the case for 
the mode line.  If this (small) breakage seems acceptable, then I think 
this is strictly better.

The alternative here is to add a call to Fkey_binding in 
note_line_or_margin_highlight to check what the down-mouse-1 binding is. 
  Let me know if that is more appropriate.  I'm just nervous because 
there are comments about Fkey_binding maybe causing GC and in general is 
seems much more heavyweight an operation for each mouse move.

   -- MJF